Penikisite
A barium-magnesium-aluminium phosphate of the bjarebyite group, discovered near Rapid Creek, Yukon.
Intro adapted from Wikipedia (CC BY-SA).
Penikisite is an IMA-recognized mineral species in the phosphate class, with the chemical formula BaMg₂Al₂(PO₄)₃(OH)₃.
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Bjarebyite structural group.
Key properties: Mohs hardness 4; specific gravity 3.79; Very pale green to white streak; Vitreous luster; optically biaxial.
IMA symbol Pks, IMA status: approved, named in 1976.
A very rare weathering product in fractures in sideritic iron formation.
It is found associated with Kulanite, quartz, siderite, fluorapatite, rapidcreekite, brazilianite, arrojadite, anatase, goyazite.
The mineral was named to honor Mr. Gunar Penikis (1936–1979), Ross River, Yukon Territory, Canada, a codiscoverer of the Rapid Creek phosphate occurrences.